I sometimes prefer to use the Russians (especially if I'm playing in a group with Newbies). The reason is because of their incredibly strategic location! In Karelia, just wait for Germany to move its navy from Germany and build (a) sub(s) and spawn them in Germany's harbor so they can't build there (with a combined effort with your allies, this is an effective strategy). Japan does prove difficult, however, but strategic placement of an IC will take care of that if Japan isn't quick. Just buy tons of infrantry at the beginning and you'll be fine (usually, in my experience).